Thin walled tubular articles of thermoplastic elastomer are known in the art to provide strong, thin, flexible protective barriers. Protective barriers having these characteristics are particularly useful to protect skin surfaces from unwanted contact or contamination and, yet, to preserve sensitivity of touch, as with condoms or finger cots used in medical examination.
U.S. Pat. No. 4,576,156, Dyck, et al., describes a condom manufactured from a variety of polyurethane thermoplastic elastomers. In the process for manufacture, a shaped mandrel is urged into the face of pre-heated, extruded elastomeric film and the film assumes the shape of the mandrel with the application of vacuum.
U.S. Pat. No. 4,684,490, Taller, et al., describes a condom manufactured from certain polyurethane thermoplastic elastomers. In the process for manufacture, a mandrel is coated with an emulsion of elastomeric material prepolymer and the coating is cured at elevated temperature.
Additional methods to manufacture condoms from thermoplastic elastomers are generally known. In one process for manufacture, the thermoplastic elastomer is blown into very thin film, the film is cut into appropriate preforms and the segments are heat sealed to form a condom.
Despite the fact that thermoplastic elastomers are taught to be suitable materials for the manufacture of the articles described above; despite the fact that these elastomers may be employed to produce a stronger, thinner and a more reliably defect free product as compared to natural rubber, the present material of choice; thin walled tubular articles are not commercially produced from thermoplastic elastomers. Each of the above described processes is unsuitable for high volume production for one or more of several reasons. For instance, the wall thickness of the resultant product may not be controllable to the desired tolerance. Also, though the product is thinner and stronger, the elastomeric modulus may be too high, i.e., the elastomer may be too stiff. Further, considering cure or annealing times required, the through-put of the machinery required may be too low.
Thus, it is an object of the present invention to rapidly produce tubular articles of thermoplastic elastomer which are soft, flexible and have a uniformly thin wall thickness.
It is also an object of the present invention to provide a method for melt forming tubular articles of thermoplastic elastomer which have a low modulus and a uniformly thin wall thickness.
It is a further object of the present invention to provide a method and hardware to draw with plug assist, tubular articles of thermoplastic elastomer which have a low modulus and a uniformly thin wall thickness.
It is another object of the present invention to provide a thermoplastic elastomer which may be drawn into tubular articles having thin walls and a low modulus.